Compressed air is commonly used to perform a myriad of functions. For example, compressed air may be used to displace water in submarine ballast tanks to increase the buoyancy of the submarine, to operate brakes on locomotives and trucks, or to pneumatically operate valves. In each case, the compressed air may include moisture and other particulate contaminates which, if not removed, may accelerate fouling, corrosion, and other interference with the equipment.
Various air dryers are known in the art to remove moisture and particulate contaminates from the compressed air. An air dryer typically includes various combinations of filters and moisture separators to clean and dry the compressed air before it reaches the equipment. For equipment that requires a continuous supply of compressed air, the air dryer may include duplicate flow paths arranged in parallel so that one flow path may remain on-line to purify the compressed air at all times while the other flow path may be taken off-line to regenerate the filters and moisture separators. The off-line flow path may be regenerated by diverting a portion of the compressed air through the off-line flow path to purge the filters and moisture separators to atmosphere and then pressurizing the off-line flow path before returning it to service.
The cycle time between the parallel flow paths and the purge time of the filters and moisture separators directly affects the anticipated lifetime of the air dryer components as well as the overall efficiency and performance of the air dryer. If the cycle time is too long, the filters and moisture separators in the on-line flow path may become excessively saturated with particulates and moisture, adversely affecting the performance of the air dryer. Conversely, if the cycle time is too short, the increased switching between parallel flow paths will result in excessive wear to the valves and other moving components in the air dryer. Similarly, an excessively long purge time wastes compressed air, and an insufficient purge time may not adequately regenerate the filters and moisture separators.
In many air dryers, the cycle time and purge time are pre-selected based on anticipated operating and ambient conditions. However, changes in the operating conditions and/or ambient conditions may result in the pre-selected cycle time and/or purge time being less than optimum. Therefore, an air dryer that utilizes operating conditions and/or ambient conditions to enhance the quality of air produced and/or reduce energy consumption would be useful.